SHANGHAI, May 15 (Reuters) - China’s central bank lowered its official yuan midpoint to a 4-1/2-month low of 6.8649 per dollar on Wednesday, amid worries over the latest escalation in the Sino-U.S. trade war.

Wednesday’s midpoint was 284 pips, or 0.41 percent, weaker than the previous fix of 6.8365 and was the softest since Dec. 27, 2018.

But market participants noted recent official fixings have persistently come in much higher than market consensus. On Wednesday, the midpoint was 142 pips firmer than Reuters’ estimate of 6.8791.

The flare-up in trade tensions has renewed global financial market concerns over how much China will allow the yuan to weaken to offset heavier pressure on its exporters. But analysts believe authorities will keep depreciation in check for now due to concerns about potential capital outflows. (Reporting by Winni Zhou and Brenda Goh; Editing by Kim Coghill)